1. Field of the Invention
This invention relates to joint assemblies for ducting and, more particularly, gimbal joints used to flexibly connect sections of ducting and, more particularly, high pressure aircraft ducting together so that the sections of ducting can swivel at the joints relative to each other.
2. Description of Related Art
Gas turbine engines produce very high pressure air which is ducted for use in various parts of the engine and/or other external applications such as in an aircraft. The high pressure ducting must often have flexible joints to accommodate the irregular internal passages of various aircraft and other hardware and machinery in which the ducting is used. To meet this requirement, sections of ducting are often connected by gimbal joints which provide the necessary flexibility during installation and operation of the ducting during engine operation. Such joints also allow the ducting limited freedom of movement when the ducting is subject to operational stresses when the engine is operating, particularly in aircraft. High temperatures and fluctuations in pressure can cause stress on the ducting and joints. Gimbal joints allow the ducting to rotate to accommodate the stresses.
Gimbal joints to accommodate high temperature high pressure flows have been developed but they have narrow areas in the middle of the joints which restricts flow and causes flow losses in the ducts. It is desirable to have a gimbal joint for high temperature high pressure flows that is light weight, compact, and strong. It is desirable to have a gimbal joint that is easy to assemble and disassemble for repair purposes. Previous designs have experienced bending of clevis lugs which have holes through which gimballing pins are disposed. Some of the bending has been so pronounced, that not only did the bending limit the amount of rotation the joint could accommodate, but pins also fell out. It is also desirable to have a very tight seal between a bellows of the seal and the forward and aft shrouds of the joint.